Hubble's main camera out of service

The Hubble Space Telescope's primary camera has blown a fuse, and its main functions seem to be gone for good.

The telescope's Advanced Camera for Surveys (ACS), an astronomical workhorse that was installed in 2002, shut down on 27 January
after suffering a power failure. Project engineers believe they have permanently lost two of the camera's three functions.
Most significantly, the camera's coveted wide-field capability has been lost, according to Preston Burch, Hubble's associate
director at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

NASA is planning to send astronauts to Hubble in September 2008, in part to install another wide-field camera and an instrument
called a spectrograph. But the ACS is unlikely to be fixed on that mission because of other pressing repairs to the telescope
itself, Burch says.

Hubble's other instruments are operating as normal.

Backup blown

“We're going back to the astronomers and asking them to re-examine their proposals.”

Preston Burch

NASA

The ACS had already been experiencing problems. It was shut down briefly last June when an electrical anomaly affected its
primary power supply. That problem was solved by switching to a backup power system (see 'Hubble back on track'). Another glitch arose in September and was also fixed.

But now the backup electrical system has blown a fuse after an unexplained spike in current, says David Leckrone of Goddard,
senior project scientist for Hubble. The problem seems to be unrelated to last year's outage, and an anomaly review board
is looking into the cause.

"It's a shame," says Adam Riess, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland. Riess had
been using the ACS's wide-field camera to study distant supernovae, exploded stars that probe dark energy — the mysterious
force pushing the Universe apart at an ever-faster rate. That work has now been sidelined, along with about two-thirds of
the proposed scientific observations for the telescope.

"We're going back to the astronomers and asking them to re-examine their proposals," says Burch. Project managers are likely
to move forward with an alternate set of observations, which was developed last November after the earlier camera failures.

The ACS has been used over the years to survey galaxies, find planets beyond our Solar System, and even to discover two moons
around Pluto, says Riess. "It's definitely had an impact on a lot of fields," he says. "It was a good camera."